#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int N = 1e5 + 10, INF = 0x3f3f3f3f;

int g[N][N], dist[N];

int n, m;

bool st[N];

int prim()
{
    memset(dist, 0x3f, sizeof dist);
    int res = 0;
    for (int i = 0; i < n; i++)
    {
        int t = -1;

        for (int j = 1; j <= n; j++)
            if (!st[i] && (t == -1 || dist[j] < dist[t]))
                t = j;

        if (i && dist[t] == INF) return INF;

        if (i) res += dist[t];
        st[t] = true;
        for (int j = 1; j <= n; j++)
            dist[j] = min(dist[j], g[t][j]);
    }

    return res;
}
int main()
{
    scanf("%d%d", &n, &m);
    memset(g, 0x3f, sizeof g);
    while (m--)
    {
        int a, b, w;
        scanf("%d%d%d", &a, &b, &w);
        g[a][b] = g[b][a] = min(g[a][b], w);
    }

    int t = prim();

    if (t == INF) puts("impossible");
    else printf("%d", t);
    return 0;
}